Development of an immunoassay for rapid screening of vardenafil and its potential analogues in herbal products based on a group specific monoclonal antibody Original Research Article

Vardenafil is a phosphodiesterase-5 (PDE-5) inhibitor for the treatment of erectile dysfunction (ED). Undeclared vardenafil and related analogues adulterated in herbal products are a threat to public health. To screen vardenafil and its analogues in herbal matrix rapidly, an immunoassay based on a group specific monoclonal antibody (McAb) was developed. Glutaraldehyde was used to link vardenafil to immunogen and coating-antigen, respectively. Through the assessment of the structural specificity of eight anti-vardenafil McAbs, the McAb of 4B9 was characterized as being specific to the common structure of vardenafil and its analogues. An indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) was established based on this McAb, the limit of detection of vardenafil was 5.0 ng mL−1, the calibration curve was linear from 5.0 to 40 ng mL−1 (R2 = 0.952) with an IC50 value of 18.2 ng mL−1. In the extracts of 20 Chinese traditional drugs, the detection capability (CCβ) of vardenafil was 0.08 mg g−1, the recoveries were 76–116% and the coefficients of variation (CV%) were 9.7%–16.2%. The ic-ELISA was in good agreement with LC-UV when detected herbal products containing vardenafil and its analogue.